Electronic devices such as smartphones may include various electronic components for performing various functions. The electronic components may be mounted on a printed circuit board, and the printed circuit board may be arranged inside the electronic device.
The electronic device may include a plurality of printed circuit boards. The forms of the printed circuit boards and the types of the electronic components mounted on the printed circuit boards may be different according to the arrangement locations of the printed circuit boards. Further, the arrangement heights of the printed circuit boards from the rear surface of the electronic device may be different. In order to compensate for the steps, in an electronic device according to the related art, rigid printed circuit boards (PCBs) may be connected to each other by using flexible printed circuit boards, and signals may be transmitted and received between the rigid printed circuit boards through signal lines formed in the flexible printed circuit boards.
In relation to a printed circuit board, when a micro-strip line or strip line for transmitting and receiving a high-frequency signal (for example, a radio frequency (RF) signal) is implemented, a distance between a signal line and a ground area may act as a factor that determines the width of the signal line. For example, as the distance between the signal line and the ground area becomes larger, the width of the signal line may become larger. Further, even though signal lines have the same impedance, transmission loss becomes lower as the widths of the signal lines become larger. However, in relation to a flexible printed circuit board, an insulation layer (for example, a prepreg layer) applied between copper foil layers used as signal lines or the ground may be omitted and an air layer may be provided, it may be difficult to maintain the thickness of the air layer at the thickness of the insulation layer due to the characteristics of the flexible printed circuit board. For example, the thickness of the air layer may have a deviation according to the coupling state of the flexible printed circuit board. The deviation of the thickness of the air layer may cause an impedance deviation of the signal lines. Further, when a distance between a signal line and a ground area is smaller as the thickness of the air layer is small, the width of the signal line is smaller than the signal line of the flexible printed circuit board, making it impossible to increase transmission loss. As another example, if a high-frequency signal is transmitted and received through a signal line formed in a flexible printed circuit board, transmission loss may be generated by a coupling phenomenon of adjacent signal lines or signal quality may be lowered due to introduction of noise signals.
In order to solve this, an electronic device according to the related art may transmit and receive high-frequency signals by using a separate transmission line, for example, a coaxial cable.
The coaxial cable may require a dedicated connector (for example, a receptacle) and a mechanism for inserting or fixing a coaxial cable. This may increase material costs, and a mounting space for other electronic components may be restricted by an arrangement space of a mechanism.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.